The primary objectives of this study is to determine the dosing regimen of DMP 266 in combination with nelfinavir in children and to study the safety profile of DMP 266 in combination with nelfinavir in children. The secondary objective is to characterize the antiviral activity (proportion of subjects below the limit of quantification of the Amplicor Assay, decrease in plasma HIV RNA level, time to nadir of plama HIV RNA levels) of DMP 266 in combination with nelfinavir in children.